15-12-2008 23:38

JVN

Re: pic: VEX High Reduction Gearbox

This is something goofy I made which is inspired by the concept of a millennium clock. I've made plenty of things which spin really fast, but I've never made something which spins VERY slow; I think this qualifies.

I use it as a lesson for Robowrangler students. I ask them to calculate some things as a way of proving they learned their gear theory.

I thought maybe someone here would think it is cool.

-John

15-12-2008 23:44

s_forbes

Re: pic: VEX High Reduction Gearbox

Hmm... I'm suddenly tempted to add a year hand to my LEGO clock.

15-12-2008 23:46

AdamHeard

Re: pic: VEX High Reduction Gearbox

Is it even possible to turn the little wheel by hand?

This is one of the most ridiculous/amazing things I've seen recently.

15-12-2008 23:51

JVN

Re: pic: VEX High Reduction Gearbox

Thanks!

No, it takes a lot of effort to turn even the 4th 60t gear from the input. I've had this gearbox sitting on my desk for a few months and every so often someone gives it a spin. Even after all this time we've been unable to advance the small wheel a noticeable amount (you can see the sharpie line we added when I first built the gearbox on the top of that wheel.)

-John

15-12-2008 23:54

Qbranch

Re: pic: VEX High Reduction Gearbox

Wow... with that kind of gear reduction... I bet you could move the Earth!

...well... provided the gears don't explode first...

Great nonsensical gizmo. I think I'll dub it the Neunian Reduction Box for my memory.

-q

15-12-2008 23:54

IKE

Re: pic: VEX High Reduction Gearbox

If my 24 hours of lemons team took this with us driving from Detroit to San Francicso, strapped on the back of the back of the race-car for the full length of the race, and then drug it back to Detroit, the little wheel would have only turned about 40 degrees.

Another way of looking at this is 1 JVN small wheel degree is equal to about 168 miles. In order words, our trip to Atlanta this spring is only 4.5 JVN small wheel degrees. That doesn't sound so bad.

15-12-2008 23:57

JVN

Re: pic: VEX High Reduction Gearbox

This is the kind of goofy stuff I make my students calculate.
It is an awesome learning aid. It makes a pretty cool piece of desk art too.

16-12-2008 00:12

MrForbes

Re: pic: VEX High Reduction Gearbox

How's that Fluids studying going? ready for the final?

Neat gearbox...in the old days cars used to have mechanical odometers. The cable driving it turns 1000 revolutions per mile. The odometer has 6 digits, the first one turns one revolution per mile. I guess it's a similar concept.

16-12-2008 00:34

sanddrag

Re: pic: VEX High Reduction Gearbox

Reminds me of something the artist Tim Hawkinson made once. A ridiculous gear reduction, where the input spun at several thousand RPM, and the output would take hundreds of years to make one revolution.

16-12-2008 01:22

Barak Shelef

Re: pic: VEX High Reduction Gearbox

haha... I was just yesterday teaching our new team members about planing a good reduction gear assembly. I'll show them this picture

16-12-2008 11:45

colin340

Re: pic: VEX High Reduction Gearbox

dang you got busted !!!!!!

thats really cool john

16-12-2008 11:55

Greg Needel

Re: pic: VEX High Reduction Gearbox

I think this is awesome. I think I am going to borrow the idea for my team, but we are going to make a "Shipdate countdown clock" So Whatever day they build it they will have to calculate the right ratio for a ~60 day output cycle.


Now the real question, has anyone ever run a vex controller for 60+ straight days using a power supply?

16-12-2008 12:02

Madison

Re: pic: VEX High Reduction Gearbox

I think the makes it reasonably possibly to accelerate the larger wheel to the speed of light.

16-12-2008 12:23

MrForbes

Re: pic: VEX High Reduction Gearbox

If not for that pesky friction....

16-12-2008 12:41

Andrew Schreiber

Re: pic: VEX High Reduction Gearbox

Also inertia

Someone please correct me if I am wrong but wouldn't you be fighting a force of 1/12(mass)(3*radius^2 + height^2) * 244140625 Newtons to get it started? Now, maybe if you put a crazy long lever arm on the small wheel's shaft you could over come that.

Of course, even that number is almost nothing compared to the real number because you would have to account for starting the gears rotating too. This could be an interesting problem for more advanced students, What is the max length of a lever arm you could attach a 100 kg weight to and still not have the large wheel move? Have them run it both ways.

But very cool John.

16-12-2008 17:55

Kevin Sevcik

Re: pic: VEX High Reduction Gearbox

What I want to know is what the backlash is at the input gear. It has to be several thousand full revolutions of the input shaft. Which amuses me to no end, given I'm usually working with gearheads that measure backlash in minutes of arc....

16-12-2008 18:04

daltore

Re: pic: VEX High Reduction Gearbox

Now try replacing all those medium gears with the large gears.

16-12-2008 18:10

Andy Baker

Re: pic: VEX High Reduction Gearbox

Cool gearbox, JVN!

We had a guy call us this past summer, wanting to use a Toughbox and a low power motor to slowly move a parabolic solar panel so that it follows the sun.

So... we found a small gearmotor package from Dayton, and used that as an input to the Toughbox. We bench tested this assembly and found out that the output shaft of the Toughbox was doing 1 revolution in about 18 minutes. Of course, this is much faster than the Earth is spinning, but it was a good way to use a very low power motor to move a 12 foot long solar panel.

AB

16-12-2008 22:41

Rupnick

Re: pic: VEX High Reduction Gearbox

Now lest see you "back-drive" that!

17-12-2008 02:14

Bannanakin

Re: pic: VEX High Reduction Gearbox

Have you seen the mini jet engines that are in the fancy rc planes? Some of those spin up to around 150,000 rpm. At that rate it would take a little over a day to turn the wheel.

17-12-2008 06:38

Mr. Freeman

Re: pic: VEX High Reduction Gearbox

It's going to move the large wheel if you apply any torque to the small wheel at all, the amount of torque just determines the acceleration, which will be tiny for any reasonable amount of mass. The only thing that might actually stop the entire thing from rotating is the friction in the bearings, which I don't think is very large.

17-12-2008 08:43

Andrew Schreiber

Re: pic: VEX High Reduction Gearbox

Thanks, you can tell it has been a while since physics.

17-12-2008 16:36

Eugene Fang

Re: pic: VEX High Reduction Gearbox

That is, before the thing starts melting or grinds itself into pieces...

18-12-2008 08:38

Libby K

Re: pic: VEX High Reduction Gearbox

Wow. This is just plain cool. =]

18-12-2008 10:01

dlavery

Re: pic: VEX High Reduction Gearbox

Heh - very cool. If you could "drive" the big wheel from the Earth to the Moon (at apogee, the approximate distance is 251,968 miles), the little wheel would turn only 4.1629 times.

-dave



.

18-12-2008 10:15

Rich Kressly

Re: pic: VEX High Reduction Gearbox

Say we're driving on the big wheel to Mars ... how many little wheel turns?

18-12-2008 11:05

dlavery

Re: pic: VEX High Reduction Gearbox

At closest approach (such as during the perihelic opposition in August 2003) the Earth-Mars distance can be as small at 34,646,418 miles. In that case, the little wheel turns 572.418 times. During conjunction, such as the one just ending this week, the distance can be approximately 247,821,000 miles. In that case, the little wheel turns 4094.437 times. I would find that number to be excessive, so for a Mars transportation application I would want to add on at least one more 12:60 reduction stage.


-dave



.

18-12-2008 16:47

AdamHeard

Re: pic: VEX High Reduction Gearbox

I would like to thank both John and Dave for finally making me understand how far away mars is

19-12-2008 20:13

Raul

Re: pic: VEX High Reduction Gearbox

All I can say is - we are such geeks!

19-12-2008 23:15

JVN

Re: pic: VEX High Reduction Gearbox

Totally... and proud of it.

Are there people out there who don't geek out over stuff like this? Weirdos...

20-12-2008 22:59

Abrakadabra

Re: pic: VEX High Reduction Gearbox

Arthur Ganson has a sculpture at the MIT museum called "Machine In Concrete" that consists of a 12-stage geartrain, where each stage reduces the speed of rotation by a factor of 50. The left end is spinning furiously at around 200 rpm; the right end is embedded in a concrete block. The end in the concrete makes one revolution every 2 trillion years or so.

Here is a partial picture of the machine from Ganson's own website:
http://www.arthurganson.com/pages/sc...te%20page.html

But to really appreciate it, you can see a video of the sculpture (and Ganson's comments about it) at the 8:30 mark in this video from the 2004 TED conference:
http://www.ted.com/index.php/talks/a...sculpture.html

21-12-2008 19:24

T3_1565

Re: pic: VEX High Reduction Gearbox

I have always wondered how fast you would need to spin something for it to spontaniously combust.... care to give it a try??

21-12-2008 20:36

Greg Needel

Re: pic: VEX High Reduction Gearbox

Along these same lines anyone care to predict what the lifespan of a vex motor constantly running would be?

22-12-2008 13:45

Rich Kressly

Re: pic: VEX High Reduction Gearbox

I don't know the answer, but we're certainly thinking about doing the same thing

21-04-2009 14:35

Rich Kressly

Re: pic: VEX High Reduction Gearbox

Thanks to senior Petra Hartman LMHS now has its own version of the JVN High Reduction Gearbox to teach gear theory to 1712 members and students in the Engineering Design classes. Woot!

http://www.chiefdelphi.com/media/photos/33863?
http://www.chiefdelphi.com/media/photos/33864?

21-04-2009 14:42

JVN

Re: pic: VEX High Reduction Gearbox

This gearbox was on display in the 148 pit in Atlanta this year. I noticed quite a few people playing with it.

21-04-2009 14:53

Andy L

Re: pic: VEX High Reduction Gearbox

I spent a few minutes playing with it, and trying to explain it's coolness to some parents, they didn't share my enthusiasm for it.

22-04-2009 13:52

Crump

Re: pic: VEX High Reduction Gearbox

i think it would be fun to make one of these gear reduction towers and make it turn once every 42 days... the 42 days is completely an arbitrary number

22-04-2009 13:57

Jared Russell

Re: pic: VEX High Reduction Gearbox

John -

In the spirit of absurdly high gear reductions, maybe next year you should put something like this on your drivetrain as soon as it is constructed. Paired with a ratcheting rectifier, you can make yourself a pretty nifty odometer. I've always been curious to know precisely how many miles a 148 robot travels in the course of build, practice, and competition...

06-07-2009 16:58

IKE

Re: pic: VEX High Reduction Gearbox

Apparently there are others outside the realm of FIRST that geek out about this too.


http://jalopnik.com/5302043/on-the-p...-transmissions

"Artist Arthur Ganson's creation called "Machine with Concrete" provides a beautiful illustration of the power of a transmission. Should you input only 1 lb-ft of torque, the other end could deliver 244 quintillion lb-ft.

Ganson's piece demonstrates the unbelievable power which can be generated through simple gear reduction. It uses an electric motor turning at a modest 200 RPM and mates it to 12 identical sets of 1/50th gear reducers for a total reduction of 1/244,140,625,000,000,000,000. Of course no material in the universe could actually deliver that kind of power without shattering into pieces and even if such materials existed, turning only one rotation at that speed would take over two trillion years. It turns so slowly that embedding the final drive in concrete will have no appreciable effect — ever. The universe itself is only about 10 billion years old, and in another 10 billion years the sun will expand into a red giant and consume the Earth anyway, the final drive having complete only 0.5% of one rotation."


My emphasis added to my favorite part.